1. Field of the Invention
The present invention relates to wire clamps for wire bonders and more particularly to a low inertia high speed voice coil driven wire clamp for use with an automatic wire bonder.
2. Description of the Prior Art
Automatic wire bonders are commercially available which provide different combinations of movable bonding heads and/or movable workstations. U.S. Pat. No. 4,266,710 shows a high speed vertically movable bonding head on an automatic ball wire bonder which cooperates with a workstation mounted on a movable X-Y table. Kulicke and Soffa Industries, Inc. of Horsham, Penna. sells a model 1482 automatic ball bonder in which the bonding head is mounted on an X-Y table.
The problem with moving the bonding head on an X-Y table is that the forces of acceleration in such high speed automatic wire bonders reach up to seven times the force of gravity. These extreme forces when imparted to the existing type of wire clamps shown in the aforementioned U.S. Pat. No. 4,266,710 cause changes in the clamping force as well as time required to open and to close the wire clamps which affects the consistency of the fine wire interconnection during a complete bonding operation. The forces may become so severe as to cause distortions in the loop trajectory and may also result in damage to the fine wire. It has been discovered that these problems result from either excessive or lack of proper wire clamp forces. Heretofore, it has been possible to slow down the speed of the X-Y table to reduce the forces of gravity which cause the aforementioed problems. However, such remedies are inconsistent with higher production rates and commercial requirements for automatic wire bonders.
It would be desirable to provide a low inertia high speed wire clamp which is not affected by the acceleration forces of a high speed X-Y table.